The embodiment relates to a naked-eye stereoscopic display apparatus having a parallax in a single dimension.
There are known technologies, in which an image on a display device such as a printing surface or a liquid crystal panel is divided into a plurality of viewpoint directions by using a special optical member such as a lenticular lens, a slit-like barrier or a lens array. Thereby, the displayed image changes according to the position of the viewer. In particular, display images (parallax images) of a same object, which are different from each other and have a specific parallax therebetween, are set to be inputted to the right eye and the left eye. In such a way, a stereoscopic display apparatus can be realized which enables the person to achieve stereoscopic vision without the need to wear special eyeglasses (hereinafter, the stereoscopic display apparatus is referred to as a “naked-eye stereoscopic display apparatus”). Note that, in this application, the direction in which the parallax images are divided is set to a single dimension in the horizontal direction.
In the case of achieving stereoscopic vision of the image in the naked-eye stereoscopic display apparatus, there is a requirement that the number of viewpoints be increased by dividing the display image as finely as possible. This is in order to expand the visual recognition range in which stereoscopic vision can be achieved, and to obtain natural stereoscopic vision and smooth motion parallax, which are worthy of long-time viewing.
Recently, for the purpose of enhancing visual attraction and visibility, application of such stereoscopic vision by parallax images to digital signage, car navigation, and the like has been studied. In the case of considering such application, there is a requirement that natural stereoscopic vision be realized by dividing the parallax images as finely as possible even in the case of using a low-resolution display device.
In order to satisfy these requirements a multi-eye type is effective, in which the viewpoints are not divided by assuming positions of eyes of an observer who observes the display device, but instead viewpoints are divided as finely as possible, and the observer views the display device at any viewpoint among the finely divided viewpoints. In order to increase the number of the parallax images, it is effective to increase the lens pitch with respect to the pixel pitch of the display device.
However, owing to a magnification effect of the lens, as the lens pitch increases color pixels look larger, and accordingly, a resolution feeling of the parallax images in the pitch direction of the lens is significantly lowered. In such a way, a malfunction occurs in that the resolution of the parallax images differs between the horizontal direction and the vertical direction.
On this subject, in Japanese Patent Laid-Open Publication No. H09-236777 (Patent Document 1), the lenticular lens is inclined with respect to the pixel array, whereby one three-dimensional pixel is composed by using not only pixels in the horizontal direction but also pixels in the vertical direction. It is reported that, in such a way, lowering of the resolution in the horizontal direction in three-dimensional displays can be suppressed, and a balance of the resolution between the horizontal direction and the vertical direction can be enhanced.
Meanwhile, in terms of cost and coexistence with two-dimensional displays, there is required a naked-eye stereoscopic display apparatus using an already widespread display device, which is composed of color pixels of R (red), G (green) and B (blue), and that has pixels of the same color arrayed regularly in the vertical direction.
In Japanese Patent Laid-Open Publication No. 2005-309374 (Patent Document 2) and Japanese Patent Laid-Open Publication No. 2006-48659 (Patent Document 3), an inclination angle of the lenticular lens with respect to the display device is conceived, and three types of color pixels are uniformly used with respect to the horizontal direction. It is reported that, in such a way, even in the case of using a display device in which the horizontally different color pixels (for example, the R, G and B pixels) are vertically arrayed in a stripe pattern, color unevenness and luminance unevenness can be reduced.
Moreover, in FIG. 1 of Patent Document 2, a configuration is introduced in which the pitch of the lenticular lens is set at 7/2 times the pixel pitch, and 7 parallax images are divided in the horizontal direction across two lenses. When the lens pitch is shifted from integral multiples of the pixel pitch as described above, the parallax images can be divided finely in many directions even if the pitch of the lens is small, and accordingly, the above-mentioned problems can be solved, and the above-mentioned requirements can be satisfied.